Mazda Faults

Tanner Diagnostician Kansas Posted   Latest   Edited  
Network Communications
2011 Mazda 3 GS 2.0L (F) 5-spd (FS5A-EL)
U0100 — Lost Communication With ECM/PCM "A"
U0101 — Lost Communication with TCM
U0401 — Invalid Data Received From ECM/PCM "A"
Can Network

Have a 2011 Mazda 3i with the 2.0 in the shop. Had the transmission rebuilt due to slipping. The Tcm has no Communication but all other modules communicate. What is interesting is the PCM connector is loose on the CAN HI CAN LO and and can witness this on the scope. But the PCM still communicates when connection is lost. And yet the TCM still does not comm, the TCM does however ground the Etm relay. Which leads me to beilieve the TCM is good (or at least somewhat functional) obviously all power and grounds have been checked at TCM. According to Data line diagram this issue to me appears it can only be between TCM and CAN splice. My confusion is with the PCM connector. Is it a possibility as it happened to me before that the diagram is wrong and the TCM CAN runs through the PCM connector then the rest of the data lines? The TCM will read codes but not display data due to no comm​.​The code in the TCM is a U0100. The code in PCM and IC are U0401 U0073. Uploaded are pics my first so apologies in advance if they dont come out right.

William Technician

Not a good CAN waveform in any of the pictures or videos for sure. U0073 shows the CAN Bus is down. IC can communicate due to the Mid-speed CAN. Check PCM and TCM powers, grounds, and ignitions. Check pin 6 and 14 for 60 ohms with vehicle off. If not 60 ohms wiring or connection issue likely. If all are fine unplug modules on the network in question one at a time until a good waveform returns…

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Stephen Technician

I notice that both green and yellow traces appear to be on a Can H lead. And that the two signals are not the same speed nor the same data pulses. The yellow trace is faster so I’m wondering if the green channel is MS CAN and the yellow is HS CAN? The yellow trace does not have correct CAN voltage even in the “good” trace. I would fix the loose issue at the PCM then retest. If still bad…

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Elias Owner/Technician

This is a very common failure of these cars, generally just the tcm is bad but connectors can fail as WELL​.​REMOVE the connector and inspect it closely.

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Tanner Diagnostician
Tanner Update

The problem eneded up being bad connections on both pcm and tcm. Fixed both connecters and communication with all modules now and CAN voltages are perfect.

Update Ð Awarded